Rivera was born in Humacao, Puerto Rico and his parents moved to Santurce, a section of San Juan, from Humacao when he was only three years old. After receiving his primary education, Rivera attended the "Escuela Superior Central de Santurce" (Central High School of Santurce). He found a part-time job at a local radio station which opened the doors to a new world for him.
Rivera became a member of the Drama Department of the University of Puerto Rico. As a drama student, he participated in two of René Marqués' plays. Having a deep baritone voice he also became a radio presenter. His radio station dramatized comedy sketches, and one of the producers suggested dramatizing Archie Comics over the radio. Due to the lack of audiovisual references for the characters at the time, there were no clear cut ways of representing the characters in Spanish, nor there were exact translations for their names. Rivera came up with the name of Yoyo Boing for representing Jughead; the name "Yoyo" sounded close to "Jughead", and the "Boing" part was a gimmick Rivera developed for the character: a vocalized "boing" that he constantly repeated to fill in silence gaps during each episode. Ever since his Archie stint on Puerto Rican radio, Puerto Ricans rarely refer to Rivera using his real name, and usually refer to him by his by-now "nickname".
1954 was the year that television was born in Puerto Rico. Rivera, together with Tommy Muñiz, José Miguel Agrelot and Paquito Cordero was one of the first comedians in Puerto Rican television. In 1960, he starred. alongside Norma Candal (Petunia) in a television comedy called "La Críada Malcríada" (The Rude Maid). In the 1970s, Rivera starred in own sit-com called "Mi Hippie Me Encanta" (I'm Crazy about My Hippie) broadcast by Telemundo. In the 1980s, Rivera starred in the situation comedies, "Generaciones", (Generations), with Chayanne, "Los Suegros" (The In-Laws) and later in a spin-off of that show called "Los Suegros y Los Nietos" (The In-Laws and the Grandchildren), broadcast by WAPA-TV. Rivera was also the General Manager of radio stations WKBM-AM ("AM 81") and WORO-FM ("Radio Oro", or Golden Radio), the radio branches of the Roman Catholic Archdiocese of San Juan.
Various media producers arranged for many Puerto Rican performers to tour New York City in the late 1950s and early 1960s. Rivera was one of these. As fate would have it, one particularly chilly evening Rivera and Bobby Capó were exiting a performance outside the Teatro Puerto Rico and were looking for a place to eat. While waiting for public transportation, Rivera told Bobby Capó two jokes. These two jokes, reinterpreted by Capó and set to music, became two major musical hits: "El Negro Bembón", for Rafael Cortijo and his Combo (sung by Ismael Rivera), and "El Caballo Pelotero", a smash hit for El Gran Combo de Puerto Rico (original version sung by Pellín Rodríguez)
In the 1990s, Rivera wrote a book titled "A Reír Con Yoyo" (Let's Laugh with Yoyo) and donated all of the proceeds to an AIDS organization. He was also active in a television show called "Desde Mi Pueblo" ("From My Town") for WIPR-TV (San Juan's channel 6), where he would visit every town and city and show all of the interesting aspects of the featured place. His co-hosts on the program were Deborah Carthy-Deu, Maria Falcon and Tony Croatto.
After José Miguel Agrelot's sudden death in 2004, the remaining co-hosts on Agrelot's long-running radio show "Tu Alegre Despertar", (Your Cheerful Wake-Up), Aurora Previdi and María Falcón, asked the radio audience to select a permanent replacement for Agrelot from a round of temporary co-hosts. Rivera won the assignment; given the wishes of Agrelot's family to achieve some closure, the program changed its name to "Contigo en el tapón" ("Along With You In The Traffic Jam") and changed its format slightly. Rivera remains as a popular co-host, filling Agrelot's considerably large shoes. He also hosts a daily program of Puerto Rican music classics at Allegro WIPR-FM.
Puerto Rican writer Giannina Braschi wrote a performance novel using the Yoyo Boing nickname as a title with some punctuation added: "Yo-Yo Boing!". Featuring a tinted photo of Rivera with overimposed X-ray specs for the book's jacket, the comic bilingual novel has very little to do with Rivera himself, but does feature a dream sequence inspired by childhood memories of the roles he played.
Rivera is currently retired from television but, at times makes special appearances. He was the protagonist of the locally produced movie for television "Santa Clos es Boricua" (Santa Claus is Puerto Rican) which was telecast in Puerto Rico and the United States through Televicentro on December 20, 2004.